Demand has risen for layer-built heat exchangers capable of using chlorofluorocarbons (CFC) and water and oil coolants in combination as first and second coolants for exchanging heat between CFC and CFC, CFC and water, water and water, or oil and water. A conventional layer-built heat exchanger is described below with reference to FIGS. 1-5 (Japanese Patent Laid-Open No. S61-243297).
As shown in the figures, the conventional layer-built heat exchanger 1 combines plural first-side plates 2, seal plates 3, and second-side plates 4 between end plates 5a and 5b. The inlet and outlet pipes 6-7 and 8-9 for the first and second coolants, respectively, are connected to the one end plate 5b.
The first-side plate 2 has a rectangular shape with a pair of round holes 10, provided offset from the center at each end of the plate, for the first coolant flow. A series of parallel and winding channels 11 are formed by dividers 12 for conducting the coolant from a position near the round hole 10 at one end of the first-side plate 2 to a position near the round hole 10 at the other end.
Holes 13 for the flow of the second coolant are formed on a diagonal line on the first-side plate 2 on the sides different from those on which the round holes 10 are formed. Each hole 13 has a rectangular shaped area 14 and a semi-circular shaped area 15 at the middle of the long side of the rectangular shaped area 14.
The second-side plate 4 has a similar rectangular shape with a series of parallel and winding channels 16 formed by dividers 17 to conduct the coolant between two round holes 18. These round holes 18 are formed corresponding to the holes 13 in the first-side plate 2, with part of each hole 18 tracing the same arc as the semi-circular shaped area 15 of the corresponding hole 13 in the first-side plate 2. Holes 19 are also provided corresponding to the round holes 10 in the first-side plate 2. Each hole 19 also consists of a rectangular shaped area 20 and a semi-circular shaped area 21 at the middle of the long side of the rectangular shaped area 20 such that part of each semi-circular shaped area 21 traces the same arc as the corresponding round hole 10 in the first-side plate 2.
The seal plate 3 has holes 22 and 23 similarly shaped to the corresponding holes 13 and 19 in the first- and second-side plates 2 and 4, respectively. The length of the rectangular shaped area 14 and 20 of the holes 13 and 19 are made long enough to cover the ends of each of the channels 11 and 16, respectively.
The plates are then assembled in successive layers in the order of first-side plate 2, seal plate 3, second-side plate 4, seal plate 3, first-side plate 2, seal plate 3, . . . as shown in the figure, and are sealed between the seal end plate 5a on one end and the end plate 5b provided with the first and second coolant inlet/outlet pipes 6-7 and 8-9.
With this construction the first coolant flows in through the inlet pipe 6, is diffused to the channels 11 of the first-side plate 2 in the rectangular shaped area of the hole 22 in the seal plate 3, and flows through the channels 11 to the hole 22 on the opposite side to flow out from the outlet pipe 7. Similarly, the second coolant flows in through the inlet pipe 8, is diffused to the channels 16 of the second-side plate 4 in the rectangular shaped area of the hole 19 in the seal plate 3, and flows out through the hole 19 on the opposite side to the outlet pipe 8.
Heat is exchanged between the first and second coolants through the seal plate 3, which is made from a material with good thermal conductivity for greater heat exchange efficiency.
With this construction, however, the distance from the ends of the channels 11 or 16 to the center of the hole 10 or 18 is long, because the channels 11 or 16 of the first-side plate 2 or second-side plate 4 are the same length and the ends of the channels form a line with respect to the hole 10 or 18. The first or second coolant must therefore travel a greater distance before it enters the channels, and coolant flow is impeded by this increased distance.
Also, when there is a pressure difference between the first and second coolants, the seal plate 3 tends to become deformed where the channels 11 of the first-side plate 2 and the channels 16 of second-side plate 4 are positioned one over the other through the seal plate 3, because the seal plate 3 is the only member separating the channels 11 and 16 of the first- and second-side plates 2 and 4. This deformation also interferes with the coolant flow. It is therefore necessary to increase the thickness H of the seal plate 3 to prevent this deformation. The overall size and cost of the heat exchanger therefore increase.
In addition, if the order of the plates is mistaken during assembly, and the seal plate 3 is omitted, leakage of the first and second coolants may occur, the offset in plate position makes assembly more difficult, and both productivity and quality decline.
In addition, to assemble the inlet/outlet pipes 6, 7, 8, and 9 to the end plate 5b, holes in the end plate 5b must be countersunk so that the inlet/outlet pipes 6, 7, 8 and 9 can be positioned.
Therefore, an object of the present invention is to provide a layer-built heat exchanger for shortening the distance between the inlet/outlet holes and channel ends in the first-side plate and the second-side plate, thus reducing the flow resistance.
A further object is to provide a layer-built heat exchanger wherein there is minimal parallel overlap between the channels of the first-side plate and the second-side plate through the seal plate.
A further object is to provide a layer-built heat exchanger wherein there is no error in the assembly order of the first-side plate, seal plate, and the second-side plate.
A further object is to provide a layer-built heat exchanger whereby positioning of the inlet/outlet pipes to the end plate is simplified.